TEM studies of the defects introduced by ion implantation in SiC

We have undertaken a systematic study of the defects formed by ion implanta tion in SiC for a large variety of experimental conditions. B, N, Al and Ne ions were implanted into 6H-SiC at room temperature RT and at 650 degrees C. Multiple energy implants were carried out in order to obtain "flat" dopa nt profiles. The samples were annealed from 1100 degrees C to 1750 degrees C for various duration times. Transmission Electron Microscopy (TEM) analys is was carried out on cross-sectional samples using weak beam dark field im aging conditions. All these defects are of interstitial type (clusters or l oops). A statistical analysis of digital images was performed to extract th e depth-distributions of the defects. The depth-distributions were compared with Monte-Carlo simulations of the ion implantation process. It is shown that when implanted at RT, the defect distributions follow the "damage" pro files i.e., defects appear in regions where atomic displacements occur in t he target. In contrast, the defects found after implantation at 650 degrees C always mirror the "range" profile before and after annealing. We show th at there is a concentration threshold under which no defect appear. These r esults are discussed in terms of point defect annihilation, clustering and dopant activation in SiC. (C) 1999 Elsevier Science B.V. All rights reserve d.